1. Field of the Invention
The present invention relates to a novel curable composition and a method of forming a pattern, specifically, a method of forming a pattern by photo-nanoimprint.
2. Description of the Related Art
In a photo-nanoimprint method, a resin thin film on a substrate is pressed with a depression pattern of a die and is cured to transfer the pattern of the die to the resin thin film. The die is called, for example, a stamper or a mold.
In the photo-nanoimprint method, since a mold (die) and a cured product (resin thin film) are in contact with each other, a large force to release them from each other, i.e., a large mold-releasing force is necessary. A larger mold-releasing force may cause defects such as a crack in the pattern of the cured product or may reduce the accuracy in alignment by floating of the substrate having the cured product from the stage on which the substrate placed. Accordingly, there is a demand for reducing the mold-releasing force.
Japanese Patent Laid-Open No. 2010-262980 discloses a gas-generating agent-containing curable composition for nanoimprint lithography.
Japanese Patent Laid-Open No. 2010-103464 discloses an imprint method using a photo-curable resin that generates a gas under at least one condition selected from heating and pressuring or reducing pressure (paragraph 0118). In the method utilizing a pressure disclosed therein, a mold is brought into contact with a photo-curable resin in a high pressure atmosphere, and then the photo-curable resin is irradiated with light through the mold and is thereby cured. Subsequently, the high pressure atmosphere is changed to a reduced pressure atmosphere. As a result, the gas dissolved in the photo-curable resin vaporizes to accumulate at the interface between the photo-curable resin and the mold. The gas (out gas) accumulated at the interface decreases the adhesion between the photo-curable resin and the mold to release them from each other. The gas-generating agent in Japanese Patent Laid-Open No. 2010-262980 generates a gas by means of light or heat and generates a gas when a polymerizable monomer in the composition is cured by light irradiation. Consequently, bubbles are generated during the curing of the composition, which leads to a transfer defect.
The method disclosed in Japanese Patent Laid-Open No. 2010-103464 uses a mechanism of generating a gas in a photo-curable resin by means of an increased pressure and a reduced pressure. Accordingly, a chamber for both pressures is necessary, and the process takes time and labor.